Science Café
A halo around the moon, the dawn, the rainbow: these are natural phenomena we have all seen at some point. But who is familiar with Bishop's ring, Lowitz arcs, the sub-sun, or the green flash? What is a mirage? And why is the sky blue?
Sixty years of observations of optical phenomena in the Netherlands.
Speaker: Peter Paul Hattinga Verschure
As diverse as they are, all these phenomena have one thing in common: they are atmospheric phenomena caused by the interplay of sunlight and moonlight with particles in the Earth's atmosphere. That is why they are called 'optical phenomena'. We encounter these color effects quite often in old weather proverbs, as many of these phenomena tell us something about the weather of today and tomorrow. There are all kinds of optical phenomena. Many are easily overlooked, but we can all observe them with the naked eye. The only thing that helps us on our way is knowing how, where, and when to look.
The Netherlands has a long history of observing these optical phenomena. For over eighty years, the KNMI collected, processed, and published observations from the public. Just as the KNMI ended this activity in 1965, a generation of young 'weather enthusiasts' began observing optical phenomena, and a new observer network was born. Now, sixty years later, this network has built an observation series that connects to the old KNMI series. In those sixty years, many insights in this field have been adjusted, and previously unknown phenomena have been observed and identified. Deventer resident Peter Paul Hattinga Verschure is the linchpin of this network and the leading expert in the Netherlands on optical phenomena in the atmosphere. In his lecture, he will not only talk about the many phenomena that can be seen, but also about the importance of the role of the observer and the processor of the observations.
Optical phenomena, in particular, turn out to be quite sensitive to misinterpretation and subjective speculation. Correctly identifying an observed phenomenon requires information, knowledge, and a certain level of experience in this multifaceted field. Furthermore, a sharp and contemplative eye, a certain spatial awareness, and the ability to describe and document the observed phenomenon very precisely are the prerequisites for careful and verifiable reporting. Conversely, the person processing the submitted observations needs the same qualities to correctly interpret those observations—which are inevitably always partly subjective in practice—for an accurate determination of the observed phenomena. Only in this way can observational data be of scientific importance.
Peter Paul Hattinga Verschure has been observing, photographing, and documenting optical phenomena since his youth. Since 1972, he has been the central point for observations in the Netherlands and provides monthly summaries in the magazine Weerspiegel of the Association for Meteorology and Climatology. He has published numerous articles in domestic and foreign journals. In 2023, his book "Optische verschijnselen in Nederland" was published, containing a complete overview of observations from 1966 to 2020. In 2025, he received the Dr. J. van der Bilt Prize from the Royal Dutch Meteorological and Astronomical Society for his complete body of work in the field of optical phenomena.
Live music will be provided by Dubio, and the moderator is Ilse Roelofsen.
